most recent 30 from http://mathoverflow.net 2013-06-19T19:06:53Z http://mathoverflow.net/feeds/user/24457 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/99709/converting-global-coordinates-into-set-of-local-matrices-for-ik-skeleton-creation Oracle3001 2012-06-15T14:24:53Z 2012-06-15T14:24:53Z

<p>I have the 3d global positions of a set of joints as they move over time and the ik skeleton structure which relates them. I am currently writing some code to convert this information in .bvh file. I understand the .bvh structure, but what I need to do for each frame is convert the global coordinates into a series of local matrices which represent the transformation to "move" from parent to child for each node.</p> <p>What I don't know how to do is calculate the local matrix for the transformation for instance to go from</p> <p>rootNode = (Rx,Ry,Rz) and lets presume that initial orientation is in line with the global axes</p> <p>to</p> <p>child1 = (Cx,Cy,Cz)</p> <p>and so on.</p> <p>Any help much appreciated.</p>

http://mathoverflow.net/questions/99626/error-metric-which-incorporates-both-mean-standard-deviation-of-data-in-euclide Oracle3001 2012-06-14T16:26:48Z 2012-06-14T16:26:48Z

<p>For simplicities sake (the actually problem is more complex)...Let say I have a set of n 3d points, whose position move over time. For all pairs, I have calculated the mean and standard deviation of the euclidean distance between them.</p> <p>I would like an error metric which incorporates the following two properties and I can use to "score" each pair in an attempt to find the "best".</p> <p>1) Pairs of points which on average over time are "close" to one another are preferred i.e small mean -> low error</p> <p>2) Pairs of points whose distance between them over time varies little i.e small standard deviation -> low error</p> <p>Furthermore, I want to be able to weight the influence of each property.</p> <p>And I am not sure of the mathematically correct way of combining these two properties.</p> <p>Any help much appreciated.</p>

http://mathoverflow.net/questions/99626/error-metric-which-incorporates-both-mean-standard-deviation-of-data-in-euclide Oracle3001 2012-06-16T15:06:32Z 2012-06-16T15:06:32Z

No it is not homework. I think you have misunderstood the question, as your answer makes no sense in that context.